APSC183 Lab 1- Density of Solids and Liquids - 2024

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Feb 20, 2024

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APSC 183 Matter and Energy II–Lab University of British Columbia Okanagan — Engineering January 2024 Lab 1: The Determination of Density and the Analysis of Uncertainty in Measurements SAFETY NOTE: To avoid hazardous accidents in the laboratory, below are some safety rules which should be followed by students and lab instructors: • Eating and drinking are forbidden in the laboratory. • SDS sheets are available in the lab. Be aware of the eyewash station and the safety shower, where it is, and how to use it. • This experiment includes handling chemicals. If there is a spill, immediately speak with your TA or Lab Technician, they can provide clean-up information. • Equipment operation must be done by following the instruction. If something is not clear, let the lab instructor or technician know to help. • Students must learn the location of first aid and fire extinguisher. In case of any fire incident, electrical equipment should be turned off before leaving the laboratory. • Un-tied long hair, loose-fitting clothes, shorts, and open-toed shoes are not permitted to be worn in the lab. • Keep the lab floor clean and dry. Students are responsible to maintain the cleanliness of the lab. • Please check the boxes beside the image, indicating you have the safety gear required and are prepared for lab.
APSC 183 Matter and Energy II–Lab University of British Columbia Okanagan — Engineering January 2024 Introduction This experiment introduces the important laboratory techniques of gravimetric analysis (weighing) and the use of volumetric glassware and the uncertainty and error analysis of laboratory measurements. Students will determine the density of two unknown liquids using volumetric glassware and determine mass using an analytical balance. The density of a solid will be determined by weighing the solid, and measuring the volume of liquid the solid displaces. The results of performing measurements multiple times will be used to use the to perform uncertainty and error analyses. Volumetric glassware is specialized glassware that has been calibrated to contain or deliver specific volumes. An example is the volumetric flask and the volumetric pipette that will be used in this lab, Volumetric glassware has one marking and will contain (volumetric flask) or deliver (volumetric pipette) a specific volume very accurately. Volumetric flask (to contain ±0.03 mL ) Volumetric pipette (to deliver ±0.02 mL) Other glassware used to measure volumes includes graduated cylinders and graduated pipettes, and burettes that have multiple markings and can be used to measure different volumes. Graduated cylinder Graduated pipette Burette
APSC 183 Matter and Energy II–Lab University of British Columbia Okanagan — Engineering January 2024 Notes for filling your burette: Lower the burette to a comfortable height for filling (around eye level) and clamp it or have your lab partner hold it. Then, holding your funnel in one hand and solution in the other, fill the burette. Record the level you filled it to, then then reclamp it at an appropriate level for dispensing fluid. You might have to lower the burette at the end to determine how much solution you used. Another piece of important equipment is the electronic balance that you will be using in your gravimetric analysis. Properly used, the balance has a possible accuracy of ±1 of the last figure displayed, as you use the balance you will notice that the last figure itself can vary within replicate samples. Reporting uncertainty or error As discussed in the lecture, there is always an associated uncertainty or error in any physical measurement. These must be reported with the result of any measurement. As an example, if you measured 25 mL with a 25 mL volumetric flask you would report the volume as 25 ± 0.03 mL (absolute) or 25 ± 0.12% (percent error) when you weigh the contents of the flask each measurement would be for example 24.999 ± 0.001 g to record the error of the balance. The other way to document uncertainty is replicate sample analyses. For this, you analyze replicate samples using the same tools and calculate an average and the standard deviation or confidence limits around that average. This method accounts for the “human” aspect in measurement, and should produce an error equal to or greater than the error associated with each specific tool. When using two tools and calculating a new value using the values you add the absolute errors if you are using addition or subtraction and you would add % errors (relative error) if you are multiplying or dividing. Since density is a value determined by dividing the mass by the volume, you will need to multiply the percent error from the volumetric flask by the percent error for the balance to arrive at the error for the density.
APSC 183 Matter and Energy II–Lab University of British Columbia Okanagan — Engineering January 2024 Laboratory Materials - 10 mL volumetric pipette and pipette pump - 50 mL burette - 25 mL volumetric flask with stopper - 10 mL graduated cylinder - 50 mL Erlenmeyer flask and rubber stopper - 50 mL beakers - Ring stand/stand for burette - Disposable pipets - Top loading balance - Glass marble - Reverse Osmosis (RO) water bottle - Small funnel - Waste liquid container (1) - Calipers - Unknown liquid - Kim Wipes - Small Steel Object Procedure The experimental data should be recorded on the Observations/Report sheet. Part 1 Liquid Density 1 1. Using an analytical balance weigh a dry beaker. 2. Using a pipet bulb, pipet into this bottle 10 mL of the unknown liquid A using a volumetric pipette. 3. Re-weigh the beaker and liquid. 4. Record this weight on your data sheet. 5. Dispose of this liquid in the liquid waste container and dry the beaker with a kimwipe.
APSC 183 Matter and Energy II–Lab University of British Columbia Okanagan — Engineering January 2024 6. Calculate the density of the liquid and its experimental uncertainty (error). 7. Repeat steps 1–6 two more times, so you have 3 measurements. 8. Calculate the average of the densities and the standard deviation around that average. Liquid Density 2 1. Using an analytical balance weigh a dry 25 mL volumetric flask with stopper or cap. 2. Using a disposable pipette, fill the flask to the graduation line with the unknown liquid A and stopper the flask. 3. Reweigh the stoppered flask on the analytical balance. 4. Empty the unknown liquid into the liquid waste container. 5. Calculate the density of the liquid and its experimental uncertainty (error). 6. Repeat steps 1–4 two more times until you have 3 measurements. 7. Calculate the average of the densities and the standard deviation around that average. Liquid Density 3 1. Obtain a 50 mL Erlenmeyer flask and rubber stopper (dry the outside of flask if necessary) and weigh on the analytical balance. 2. Fill the burette with your unknown liquid A. Burette 15 mL of the unknown liquid into the Erlenmeyer flask, put the stopper back, and reweigh. 3. Without emptying the flask add another 15 mL and reweigh. 4. Repeat step #3 until you have three measurements. 5. Calculate the density for each addition and their experimental errors. 6. Repeat 1 to 5 with unknown liquid B. Part 2 Solid Density 1 – solid object with a known volume 1. Student 1 a. Measure the diameter of the glass marble with a micrometer and calculate its volume. b. Place a paper weighing boat on balance. Tare the boat. c. Wipe all fingerprints off of the glass marble, place it in the weighing boat on the analytical balance, and record the weight of the glass marble. d. Calculate the density of the glass marble. 2. Student 2 a. Repeat steps a–d above
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